<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>05清除浮动</title>
    <style>
        /* #box1 {
            width: 100px;
            height: 100px;
            background: red;
            float: left;
        }
        
        #box2 {
            width: 200px;
            height: 200px;
            background: blue;
            clear: left;
        } */
        /* #box1 {
            width: 200px;
            border: 1px black solid;
        }
        
        #box2 {
            width: 100px;
            height: 200px;
            background: red;
            float: left;
        }
        
        .clear {
            clear: both;
        } */
        
        #box1 {
            width: 200px;
            border: 1px black solid;
        }
        
        #box2 {
            width: 100px;
            height: 200px;
            background: red;
            float: left;
        }
        
        .clear:after {
            content: '~~';
            clear: both;
            display: block;
        }
    </style>
</head>

<body>
    <!-- <div id="box1"></div>
    <div id="box2"></div> -->
    <!-- <div id="box1">
        <div id="box2"></div>
        <div class="clear">这是一个空标签</div>
    </div>
    aaaaa -->
    <div id="box1" class="clear">
        <div id="box2"></div>
    </div>
    aaaaa
</body>

</html>